Familial cancer syndromes provide a unique opportunity to examine the mechanism of inherited susceptibility to cancer, as well as the more general processes involved in the development of malignancy. Our laboratory is studying a family with Li-Fraumeni syndrome, which is characterized by the development of diverse neoplasms as multiple primary tumors within single individuals. Particular emphasis has been placed on the role of oncogenes in the development of these tumors. Oncogenes are genes involved in the development of malignancy. Oncogenes derive from normal cellular genes, termed proto-oncogenes, when the latter are altered by point mutation, deletion, rearrangement, or amplification. Evidence for the involvement of oncogenes in non-inherited human malignancy, as well as in inherited predisposition to cancer, continues to accumulate. The normal functions of several proto-oncogenes have been elucidated; they are involved in normal cell growth, division, metabolism, and/or differentiation. Proto-oncogene products functions as growth factors or growth factor receptors, tyrosine-specific or serine/threonine-specific protein kinases, G-proteins exhibiting GTPase activities, or nuclear proteins participating in DNA synthesis. In this application, we propose to study the involvement of proto-oncogene(s), oncogene(s), and suppressor genes in the predisposition of the members of a cancer-prone family. Our goal is to identify and characterize the primary genetic defect shared in this family; however, in this process, we may have uncovered certain oncogenes which may represent secondary and tertiary genetic defects. We will (1) continue to analyse two transforming genes derived from the normal skin fibroblasts of two affected family members, the proband, and his brother, (2) attempt to identify the transforming gene(s) in normal skin fibroblasts of other family members, and (3) assess the possible involvement of a suppressor gene, Rb, in the family genetic defect. The oncogene will be molecularly cloned and compared to their normal counterparts. The genetic defect will be defined by DNA sequence analysis and site-directed mutagenesis. Specific antibodies will be raised to synthetic peptides and the biosynthesis and subcellular localization of the oncogene product will be examined. Attempts will be made to characterize the oncogene product and to explore its function. RNA profile of the Rb gene in normal skin fibroblasts of the family members will be examined by Northern analysis. Rb DNA RFLPs will be detected by Southern hybridization.